NEW_Accomplishments.indd - IRIS

2006 IRIS 5-YEAR PROPOSAL UPWELLING AND DOWNWELLING
Receiver Function Analysis of the Nicoya Peninsula, Costa Rica
Claudia Flores, Susan Schwartz • University of California, Santa Cruz
CRSEIZE (Costa Rica Seismogenic Zone Experiment) was a collaborative effort to identify and describe subduction
zone processes occurring on the southern section of the Middle American Trench. This experiment consisted of deployed
standard IRIS/PASSCAL three-component broadband
and short period instruments on land as well
as three-component broadband ocean bottom seismometers
and hydrophones, and geodetic surveying
throughout Costa Rica.
Receiver function analysis using time-domain
deconvolution techniques (Ammon,1991; Ligorría
and Ammon,1999) is applied to broadband
data collected during CRSEIZE to constrain the
depths to major boundaries such as the top of the
subducting slab, the oceanic crust-mantle interface
of the slab, and the base of continental crust in
the overlying plate. Previous tomography studies
using CRSEIZE data (Deshon, 2004; Deshon
and Schwartz, 2004) suggest the existence of a
serpentinized forearc mantle wedge and a change
in the location and depth of the seismogenic zone
from north to south beneath Nicoya Peninsula.
With receiver function analysis, we hope to verify
the depth and range of this mantle wedge and find
other characteristics of the slab-plate interface
where interplate earthquakes occur. Current work
suggests that the velocity contrast resulting from
the slab-continental crust interface seems to be
reduced as you move away from the trench. Other
Map of CRSEIZE broadband stations located on land (red triangles) and
ocean bottom (blue triangles) on and offshore Nicoya Peninsula, Costa Rica.
arrival phases, such as PKP(AB), and statistical
analysis of all receiver functions will be
used to improve the quality and reduce the
uncertainty of our final results.
Ammon, C. J., The isolation of receiver effects from
teleseismic P waveforms, Bull. Seismol. Soc. Am, 81,
2504-2510, 1991.
Deshon, H. R., Seismogenic zone structure along the
Middle America subduction zone, Costa Rica, Ph.D.
thesis, 356, pp., Univ. of Calif. Santa Cruz, 2004.
Deshon, H. R., and S. Y. Schwartz, Evidence for serpentinization
of the forearc mantle wedge along the
Nicoya Peninsula, Costa Rica, Geophys. Res. Lett.,
31, doi:10.1029/2004GL021179, 2004.
Ligorría, J. P. and Ammon, Iterative deconvolution and
receiver-function estimation, Bull. Seismol. Soc. Am,
89, 1395-1400, 1999.
Plot of receiver functions with respective distance from trench increasing going down.
Receiver functions are shown in black for one event at recording stations and red for
stacked receiver functions at respective stations (note: stations COND and PAPA are
combined).
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